NATATORES. 473 



the wing being necessary to sustain it during the raging of 

 of the gale, it then moves with zigzag turns of great swiftness, 

 ascending the billows, topping their surgy summits, and de- 

 scending into the gulf between, where a momentary shelter 

 enables it to gain fresh vigom% and seize from the slanting 

 surface any floating mollusks that may present themselves, 

 and which, from the disturbed state of the sea, are apparently 

 more abundant then than at other times. 



The plumage of all the members of this genus is dense, 

 thick, and extremely hght; hence their bodies are much 

 smaller than they appear to be. The average weight of seve- 

 ral examples of this species was five ounces. Although the 

 present bird and Prion banksii were seen in company, as 

 before stated, the differences between the two were very ob- 

 servable, the°extreme delicacy of colouring and the smaller size 

 of the F. turtur strongly contrasting with the more bluff and 

 darker-coloured head of the P. banhsii ; when the wings were 

 expanded, the black mark, similar to the letter W, was 

 equally conspicuous in both. 



All the upper surface dehcate blue-grey ; the edge of the 

 shoulder, the scapularies, outer margins of the external prima- 

 ries and the tips of the middle tail-feather black ; small spot 

 before the eye and a stripe beneath black ; lores, line over, 

 beneath, and behind the eye and all the under surface white, 

 stained with blue on the flanks and under tail-coverts ; bill 

 light blue, deepening into black on the sides of the nostrils 

 and at the tip, and with a black line along the side of the 

 under mandible ; irides very dark brown ; feet beautiful 

 light blue. 



Sp. 642. PRION ARIEL, Gould. 



Fairy Prion. 

 Prion ariel, Gould in Ann. and Mag. of Nat. Hist., vol. xiii. p. 366. 



This is one of the smallest species of the genus, being much 

 less than P. ttirtur and its near ally the P. brevirostris of the 



